<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        h2 {
            text-align: center;
        }

        .box {
            width: 600px;
            margin: 50px auto;
            display: flex;
            font-size: 25px;
            line-height: 40px;
        }

        .qs {

            width: 450px;
            height: 40px;
            color: red;

        }

        .btns {
            text-align: center;
        }

        .btns button {
            width: 120px;
            height: 35px;
            margin: 0 50px;
        }
    </style>
</head>

<body>
    <h2>随机点名</h2>
    <div class="box">
        <span>名字是：</span>
        <div class="qs">这里显示姓名</div>
    </div>
    <div class="btns">
        <button class="start">开始</button>
        <button class="end">结束</button>
    </div>

    <script>
        // 数据数组
        const arr = ['马超', '黄忠', '赵云', '关羽', '张飞']
        // 获取dom元素
        // 开始
        const start = document.querySelector('.start')
        // 结束
        const end = document.querySelector('.end')
        // 显示结果
        const qs = document.querySelector('.qs')
        // let timer = 0
        let flag = true
        // 分别给2个dom对象注册点击事件
        start.addEventListener('click', function () {
            // 定时器
            if (flag) {
                timer = setInterval(function () {
                    // 获取随机数
                    const random = parseInt(Math.random() * arr.length)
                    qs.innerHTML = arr[random]
                }, 100)
                // console.log(timer);
            }
            flag = false

        })
        // 关闭
        end.addEventListener('click', function () {
            // 关闭定时器
            clearInterval(timer)
            flag = true
        })


    </script>
</body>

</html>